Mark Scheme (Results) November 2010

Transcription

1 Mark Scheme (Results) November 200 IGCSE IGCSE Physics (4420) Paper 2H Edexcel Limited. Registered in England and Wales No Registered Office: One90 High Holborn, London WCV 7BH

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3 IGCSE PHYSICS 4420/2H November 200 The following abbreviations have been used aps dna dop ecf owtte accept phonetic spelling do not allow dependent on previous error carried forward or words to that effect

4 (a) voltage = current x resistance or any transposed version V = I x R allow symbols (b)(i) charge/electrons /coulombs dna ions (b)(ii) lower/less/smaller/weaker/not as strong dna slower or slows down (c)(i) variable resistor/rheostat dna just resistor (c)(ii) ammeter Y 0.8 (A) ammeter Z.2 (A) (d)(i) (d)(ii) parallel any one of lights can be switched on/off independently if a light fails the others will remain on lights may not fade as extra light switched on dna same brightness

5 2(a)(i) 2(a)(ii) 2(b) any one of (left to right) decreasing wavelength right to left, increasing wavelength (left to right) increasing frequency right to left, decreasing frequency speed can travel through vacuum can all be reflected/refracted/polarised/ diffracted/interfere can all transmit energy speed of 300 million m/s allow same velocity microwaves internal heating all correct (3) infra-red. skin burns ultraviolet damage to surface gamma mutations and any two or three correct any one correct (3) 2(c) (satellite)/(tele)communications transmit data heating if qualified mobile phone/wireless network dna signals in fibre optics GPS radar

6 3(a)(i) 3(a)(ii) 3(a)(iii) 3(b) electron(s) not regular/irregular/not constant /erratic/not steady/unpredictable /no set pattern Allow emit different number every time Geiger Muller/GM tube/counter / cloud chamber / gamma camera / spark counter allow Geiger counter/detector time from two appropriate activities shown clearly on the graph 200 (million years) or ± 0 (million years

7 4(a)(i) 4(a)(ii) chemical kinetic 4(b)(i) 25 watts / W / J/s allow for clear indication that 4 min = 240 s 4(b)(ii) 7500 J/min (3) 7500 W 7500 efficiency = useful (energy) output ( 00%) total (energy) (output/input) allow in terms of power and directly proportional (3)

8 5(a)(i) 0. (s) or /0 (s) allow for a time interval of five 5(a)(ii) 730 mm/s allow ecf from part ai allow for clear indication that (average) speed = distance time (taken) 5(b) centre of X at the start of the downwards arrow judge by eye

9 6 N S on either diagram S N N S S N 7(a)(i) either -273 ( C) or minus 273 ( C) do not credit just 273 7(a)(ii) 293 or ecf ai +20 and addition correct credit with either or ai +20 7(b)(i) 7(b)(ii) speed/velocity/kinetic energy/ke /movement (energy)/momentum /collisions dna pressure/temperature/volume/ energy/vibration increases/gets bigger stays the same/does not change

10 8(a)(i) (total) clockwise moment(s) = (total) anticlockwise moment(s) allow turning effect for moment dna sum of clockwise = sum of anticlockwise allow force distance is the same on both sides of the fulcrum/turning point/line allow moment same on both sides dna turning force for moment 8(a)(ii) 8 (kn) allow for clear indication that weight (of concrete block) x 8 = 24 x 6 8(b)(i) weight = mass g W = mg or any correctly transposed version 8(b)(ii) 2600 kg allow for clear indication that mass = any weight tonnes /t (3) e.g kg (3)

11 9(a) friction allow drag/air resistance 9(b)(i) F = ma or any transposed version words or symbols 9(b)(ii) reference to net/resultant force or difference in the forces acting or push force friction ignore not balanced and total 9(b)(iii) a = 50/200 = 0.25 allow 8 m/s 2 ignore N/kg 9(c) slope = acceleration or use of any v/t from graph slope shown to be about 0.25 or use v = at and compare with v value from graph ecf from (b)(iii)

12 0(a)(i) 0(a)(ii) proton/atomic (number) nucleon/mass (number) (number of) neutrons and protons 0(b)(i) 4 0 all correct 7 0(b)(ii) have a different number of protons ignore not same element & reference to electrons and atomic number 0(c)(i) alpha : completely absorbed/stopped by paper gamma : will not be affected by paper or can easily pass through paper 0(c)(ii) longer would remain active for longer /would need replacing less often d.o.p. ignore don t need to replace regularly

13 (a)(i) gold uranium (a)(ii) nuclei positive alpha positive positive/like charges repel neutron uncharged/neutral hence not repelled any four (4) (b) mass weight/size ignore density (c) (d) increase probability of fission/absorption or fast-moving neutrons won t cause fission/are not absorbed ignore reference to collisions absorb neutrons mark both parts together control the (rate of) reaction or speed up and slow down the (rate of) reaction ignore: stop reaction

14 2(a) blow down right hand tube/use a pump/add more liquid/raise right hand tube dna increase temperature as it is a Boyle s law expt 2(b)(i) = p 520 p = 95 (kpa) 2(b)(ii) constant temperature fixed mass/number of molecules /no leaks dna fixed mass of liquid 2(c)(i) random fast (moving) ignore faster 2(c)(ii) idea of collisions with liquid s surface ignore push

15 3(a)(i) direction in which a (free) north pole would point allow from north to south dna direction of magnetic field 3(a)(ii) correct arrow on one other line any incorrect arrow (0) 3(b)(i) 3(b)(ii) 3(c)(i) 3(c)(ii) thumb - force first finger- (magnetic)field second finger- current 3 correct correct motor loudspeaker arrow pointing down the page increase current ignore use of coil, thicker wire and more voltage increase magnetic field / use stronger magnets / put magnets closer together ignore bigger magnets

16 4(a)(i) 0.5 x 0 x 3.8 mgh scores 4(a)(ii) Z 4(b)(i) 6 (J) 9 3 4(b)(ii) ½mv 2 v = 8 (m/s) ecf from (b)(i) 4(c) gpe 9 (J) ke 6 (J) heat/thermal 3(J) ecf their ke from (b)(i) correct names or correct numbers ignore input, useful output and wasted if smaller output assigned to larger arrow and otherwise correct

17 5(a)(i) both incident ray completed and a refracted ray drawn and both labelled normal drawn correctly (by eye) both sides of boundary and labelled rays drawn correctly angles labelled correctly (4) 5(a)(ii) 5(b)(i) ray box/any source of light curved glass block pins protractor paper ruler any two ignore pencil/pen n = sin i / sin r 5(b)(ii).5(3) no ecf from (b) sin 50/sin 30 5(b)(iii) idea of a greater percentage uncertainty /idea of angle very small compared to uncertainty allow less sig fig (in raw data) dna smaller angles are less accurate/harder to measure

18 6(a) 50 period = 0.02 (s) Hz (3) 6(b)(i) 340 (m/s) 0.680/0.002 use of v = fλ scores 0 6(b)(ii) loudness/volume ignore intensity 6(b)(iii) A louder than B (ora) B further from source of sound (ora) wave dissipates energy as it travels/energy less as wave spreads out any two

19 7(a) coal, gas, oil, uranium allow fossil fuels and nuclear ignore petrol 7(b)(i) 7(b)(ii) 7(c) doesn t depend on weather no greenhouse gases requires little space renewable any two limited sites harmful gases/minerals brought up need to drill deep holes long time to (survey and) build any two wind solar/sunlight wave hydroelectric any two dna tidal ignore water

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